c++ - Easily measure elapsed time

Question

I am trying to use time() to measure various points of my program.

What I don't understand is why the values in the before and after are the same? I understand this is not the best way to profile my program, I just want to see how long something take.

printf("**MyProgram::before time= %ld
", time(NULL));

doSomthing();
doSomthingLong();

printf("**MyProgram::after time= %ld
", time(NULL));

I have tried:

struct timeval diff, startTV, endTV;

gettimeofday(&startTV, NULL); 

doSomething();
doSomethingLong();

gettimeofday(&endTV, NULL); 

timersub(&endTV, &startTV, &diff);

printf("**time taken = %ld %ld
", diff.tv_sec, diff.tv_usec);

How do I read a result of **time taken = 0 26339? Does that mean 26,339 nanoseconds = 26.3 msec?

What about **time taken = 4 45025, does that mean 4 seconds and 25 msec?

Answer 1

//***C++11 Style:***
#include <chrono>

std::chrono::steady_clock::time_point begin = std::chrono::steady_clock::now();
std::chrono::steady_clock::time_point end = std::chrono::steady_clock::now();

std::cout << "Time difference = " << std::chrono::duration_cast<std::chrono::microseconds>(end - begin).count() << "[μs]" << std::endl;
std::cout << "Time difference = " << std::chrono::duration_cast<std::chrono::nanoseconds> (end - begin).count() << "[ns]" << std::endl;